Calorimetry is the measuring of heat absorbed or evolved in endothermic and exothermic processes, respectively, such as chemical reactions, changes in states of matter, or the mixing of substances to form solutions. Calorimetry is applicable within a wide variety of disciplines such as in biological systems, the pharmaceutical industry, the chemical industry, and so on. Calorimeters provide essential thermodynamic information about substances such as heat capacity, enthalpy and temperature. Calorimeters are used to generate data curves of temperature versus heating that can be analyzed to provide quantitative information about substances of interest. Large-scale calorimeters have been available for many years to provide such thermodynamic information. However, large-scale calorimeters typically involve the use of relatively large substance sample volumes (e.g., on the order of hundreds of microliters), low heating and cooling rates, and long measurement times (e.g., on the order of tens of minutes).
Efforts to make calorimeters more time and cost effective are ongoing. Small-scale calorimeters have various advantages over large-scale calorimeters, such as reduced sample volumes that enable faster heating and cooling rates, decreased measurement times, and lower costs associated with power and sample consumption. One area of development in small-scale calorimeters is with microfluidic devices. Microfluidic devices provide miniaturized environments that facilitate the use of very small sample volumes. Microfabrication techniques enable the fabrication of small-scale microfluidic calorimeters on a chip, called “chip calorimeters”, that are capable of analyzing small sample volumes on the order of tens of picoliters.